<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
        class App{
            show(){
                console.log(this);
            }
        }
        var a=new App()
        var b=a.show;
        this.b();
        b();
    </script>
</head>
<body>

</body>
</html>